This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A036522 #12 Mar 22 2020 17:31:18 %S A036522 15,55,5565,255255,12552555,585555531,5355555765,50525595555, %T A036522 5258558551555,555595555515,1551745755555555,39355555555552515, %U A036522 552550545955255555,13555559555595513555,455557505555605555585,5555558514557555255755,555457555855555784555355,505555585555455555505395 %N A036522 Smallest triangular number containing exactly n 5's. %t A036522 nsmall = Table[Infinity, 20]; %t A036522 For[i = 0, i <= 10^6, i++, p = PolygonalNumber[i]; %t A036522 n0 = Count[IntegerDigits[p], 5]; %t A036522 If[nsmall[[n0]] > p, nsmall[[n0]] = p]]; %t A036522 ReplaceAll[nsmall, Infinity -> "?"] (* _Robert Price_, Mar 22 2020 *) %Y A036522 Cf. A048360, A036517-A036526. %K A036522 nonn,base %O A036522 1,1 %A A036522 _David W. Wilson_ %E A036522 a(13)-a(18) from _Giovanni Resta_, Oct 30 2019